1. Field of the Invention
The present invention relates to iron-cobalt alloys especially those iron-cobalt alloys containing between 5 and 35% cobalt and which do not undergo an order-disorder transformation phenomenon during heat treatment. The alloy is characterized by a cube-on-face texture which may be described in terms of Miller Indicies as (100 ) [001] and which also has a primary recrystallized microstructure and normal grain growth. The process for obtaining such cube texture involves either a single or a multiple cold working and the alloys which are produced therefrom find particular use as a magnetic core material for aircraft generators where such rotating machinery is improved by the magnetic laminations having a double orientation of the grain structure.
2. Description of the Prior Art
Great effort has been expended in recent years particularly in the aerospace industry to produce smaller and lighter weight electrical equipment. This has led to increased operating inductions in the magnetic core materials of aircraft electrical generators where, in some designs, cube or doubly oriented silicon steel has replaced nonoriented silicon steel.
Current and future advanced designs are contemplating the use of a 50% cobalt-iron alloy which is presently being marketed by the Westinghouse Electric Corporation under the trademark "HIPERCO 50". This alloy permits higher operating inductions than the 31/4 % silicon iron because of its higher saturation value, namely about 24,000 gauss, as well as the low magnetocrystalline anisotropy. However, one of the main deterrents to wider use of the 50% cobalt-iron alloy is its high cost arising from the 50% cobalt content and the difficulty in cold rolling this alloy resulting from the fact that iron-cobalt alloys containing in excess of about 35% cobalt undergo, during heat treatment, a transformation phenomenon which is known as an order-disorder phenomenon. This transformation results in the production of an exceedingly brittle material which poses an extreme amount of difficulty in cold working. In order to suppress this transformation phenomenon and its resulting brittleness, elaborate steps must be taken to quench the iron-cobalt alloy, containing in excess of 35% cobalt, in ice brine before the material has a chance to transform.
Alloys in the 20 to 30% cobalt range, which have saturation values similar to the 50% cobalt-iron, can be much more readily processed. However, these alloys do not normally possess an oriented structure as commercially produced and consequently, high inductions at low field strengths have not been previously observed in these alloys because of their high positive anisotropy values.
The present invention alleviates the shortcomings of the prior art compositions and provides an alloy and a method for manufacturing the same which results in the attainment of a useful degree of cube texture or double orientation in cobalt-iron alloys having between about 5% and about 35% cobalt which alloys can be most easily cold worked. The present alloy leads to higher operating inductions than can now be obtained in the cube oriented 31/4 % silicon-iron alloys or in the non-oriented alloys with similar cobalt contents.